Hyperventilation-induced changes of blood cell counts depend on hypocapnia

Area of Science:

• Physiology
• Respiratory Medicine
• Hematology

Background:

• Voluntary hyperventilation can alter blood parameters like cell counts and concentration.
• The underlying mechanisms, whether related to blood gas changes or respiratory muscle work, require clarification.

Purpose of the Study:

• To determine if hyperventilation-induced hematological changes are caused by altered blood gases or respiratory muscle exertion.
• To investigate the role of hypocapnic alkalosis in these physiological responses.

Main Methods:

• Healthy students underwent 20-minute hyperventilation using normal air or air enriched with 5% carbon dioxide (CO2).
• Blood gas levels, hematocrit, white blood cell counts, platelet counts, and plasma catecholamines were measured.
• Changes were compared between the two breathing conditions.

Main Results:

• Hyperventilation with normal air significantly decreased partial pressure of CO2 (P < 0.001), leading to hemoconcentration (P < 0.01), increased lymphocytes (P < 0.001), and elevated platelet counts (P < 0.01).
• Breathing CO2-enriched air minimized these changes, indicating blood gas alterations are key.
• Plasma adrenaline and noradrenaline levels significantly increased with normal air hyperventilation (P < 0.001) but not with CO2-enriched air.

Conclusions:

• The observed hemoconcentration, increased white blood cell and platelet counts, and elevated catecholamines during hyperventilation are direct consequences of hypocapnic alkalosis.
• Respiratory muscle work alone does not appear to drive these specific hematological and hormonal changes.